/Engine/Source/Runtime/Core/Public/Algo/IndexOf.h
Returns the index of the first element in the range whose projection is equal to the given value.
The index of the first element found, or (SizeType)-1 if none was found (where SizeType = decltype(GetNum(Range)))
namespace Algo { template<typename RangeType, typename ValueType, typename ProjectionType> auto Algo::IndexOfBy ( RangeType && Range, const ValueType & Value, ProjectionType Proj ) }